If you like Attack on Titan, be sure to check out these other user recommended anime that are similar to Attack on Titan.

spice
While they are completely different settings, both anime take place in very violent worlds. Both feature a main character who must make life-or-death choices, and has to go through traumatizing experiences.

spiceHighschool of the Dead and Attack on Titan are both anime showing humans battling man-eating creatures/monsters and just trying to survive against overwelming odds. Both are great post-apocalyptic shows.